QUASI-DIRECT NARROW GASB-ALSB (100) QUANTUM-WELLS

In GaSb-AlSb quantum wells, GaSb is expected to make a transition to an X-valley semiconductor for well widths less than 2 nm. For narrow X-valley quantum wells the unassisted radiative transitions are no longer forbidden, allowing for the possibility of a ''quasi-direct'' transition from the X conduction band to the F valence band. Photoluminescence characterization of such narrow well GaSb-AlSb multi-quantum well structures has been performed. Spectra from wells as thin as a few monolayers were observed. A comparison of the measured transition energy with a simple calculation supports the idea that the observed transitions are indeed quasi-direct transitions.